Polyesters and their preparation



United States Patent ice POLYESTERS AND THEIR PREPARATION Rupert C.Morris, Berkeley, Vernon W. Buls, Walnut Creek, and George W. Conklin,Oakland, Calif., assignors to Shell Development Company, New York, N.Y., a corporation of Delaware No Drawing. Application July 1, 1954Serial No. 440,864

15 Claims. (Cl. 260-75) This invention relates to polyesters and theirpreparation. More particularly, the invention relates to a new class ofimproved polyesters prepared from polynuclear polycarboxylic acids andto the utilization of these polyesters, particularly in the preparationof fibers and filaments and improved coating compositions.

Specifically, the invention provides new and particularly usefulpolyesters comprising polyesters of polycarboxylic acids having at leastthree six-membered carbocyclic rings separated by bivalent aliphaticradicals and having at least two carboxyl' groups attached to difierentcarbocyclic rings, such as, for example, dicarboxydibenzylbenzene, andpolyhydric alcohols. The invention also provides improved coatingcompositions prepared from the above-described polyesters, andparticularly those prepared from polyhydric alcohols containing at leastthree hydroxyl groups.

As a special embodiment, the invention also provides certain newaliphatic polycarboxylic acids possessing at least three six-memberedcycloaliphatic ring-s separated by bivalent aliphatic radicals andhaving at least two carboxyl groups attached to different cycloaliphaticrings.

This application is a continuation-in-part of our application Serial No.249,626, filed October 3, 1951, now abandoned.

It is an object of the invention to provide a new class of polyesters.It is a further object to provide new polyester-s prepared frompolycarboxylic acids having a plurality of carbocyclic rings attachedthrough bivalent aliphatic radicals. It is a further object to providenew polyesters which have unusually high melting points and areparticularly useful in the formation of heat resistant synthetic fibersand filaments. It is a further object to provide new polyesters whichare valuable as plasticizing agents. It is a further object to providenew polyesters that can be used to give improved coating compositions.It is a further object to provide new cycloaliphatic polycarboxylicacids having properties which may then be particularly useful andvaluable in industry. These and other objects of the invention will beapparent from the following detailed description thereof.

It has now been discovered that these and other objects may beaccomplished by the polyesters of the invention comprising polyesters ofpolycarboxylic acids having at least three six-membered carbocyclicrings separated by bivalent aliphatic radicals and having at least twocarboxyl groups attached to different carbocyclic rings, and polyhydricalcohols. These polyesters have been found to possess many unusualproperties which make them particularly useful and valuable in industry.The linear polyesters prepared from the dihydric alcohols may, forexample, be drawn into fibers that can be oriented by cold drawing. Theresulting fibers are hard and pliable and have excellent heat stability.The fibers prepared from these polyesters, for example, do not decomposeat temperatures below about 375 C. to 400 C., while many of thecommercial polyester fibers decompose at temperatures below 300 C.

2,823,197 Patented Feb. 11,

The polyesters prepared from alcohols having three or more hydroxylgroups, such as, for example, glycerol, pentaerythritol, andhexanetriol, have been found to be particularly outstanding ascomponents for coating and impregnating compositions. They areespecially valuable as additives for lacquers and enamels containingureaaldehyde and melaminealdehyde resins as they tend to impartincreased hardness and durability thereto.

The polycarboxylic acids, polyesters of which are provided by thepresent invention, comprise those acids having at least threesix-mcmbered carbocyclic rings separated by bivalent aliphatic radicalsand having at least two carboxyl groups attached to differentcarbocyclic rings. The carbocyclic rings may be aromatic orcycloaliphatic and, if cycloaliphatic, may be saturated or unsaturated.The rings may also be substituted, if desired, with other substituents,such as halogen atoms, alkoxy radicals and the like. The acidspreferably contain only two carboxyl groups but may contain three, fouror more such groups. Examples of these acids include, among others,dicarboxydibenzylbenzene, di(carboxyphenylethyl) isopropylbenzene,di(carboxybenzylphenyl)methane, dicarboxydibenzylchlorobenzene,di(carboxychlorophenyl)benzene, di(carboxycyclohexylmethyl)cyclohexane,di(carboxycyclohexylmethyl)isopropylcyclohexane,di(carboxycyclohexylmethylcyclohexyl)methane,di(carboxycyclohexenylmethyl)cyclohexene, anddicarboxydicyclohexylchlorocyclohexane.

Preferred polycarboxylic acids are those of the formulae:

wherein X is a cycloaliphatic bivalent radical or aromatic bivalentradical or a chloro or alkyl substituted derivatives thereof wherein thetwo free valences are in the No. l and 4 positions on the 6-memberedcycloaliphatic or aromatic ring in the said radicals, and n is aninteger from 1 to 5.

Coming under special consideration, particularly because of the fineproperties of their polyesters as plasticizers are the cycloaliphaticacids, and particularly those of the formulae:

21100 0C -orno1+ G The halogenated alkyl aromatic acids used in thisprocess may be conveniently prepared by halongenating the correspondingalkyl-substituted aromatic acid in the presence of a catalyst, such asultraviolet light, that'is known to promote the halogenation in the sidechain. Chloromethylbenzoic acid may be prepared by this method, forexample, by bubbling chlorine into a reaction medium containing toluicacid in the presence of ultraviolet light, preferably having a wavelength between 1000 and 6000 Angstroms.

Alkyl-substituted aromatic acids that may be used in the halogenationreaction may be exemplified by toluic plified by benzene, toluene,isopropylbenzene, xylene, tertbutylbenzene, naphthalene, butylbenzene,methyl benzene, and the like.

The condensation is accomplished by heating the components together,preferably in the presence of a Friedel- Crafts metallic halidecatalyst. Suitable catalysts of this type include ferric chloride,aluminum chloride, zinc chloride, stannic chloride, boron fluoride,copper chloride, zirconium tetrachloride, titanium tetrachloride, andaluminum bromide. The catalyst may be employed as such or in solution orother highly dispersed forms. The addition compounds of the metalhalides with water, alcohol, ether acids, etc., may also be used. Theamount of the catalyst employed will vary over a wide range dependingupon the particular reactants and conditions employed. In most cases,the catalyst will be used in amounts varying from 1% to by weight of thereactants, and more preferably from 2% to 5% by weight of the reactants.

The amount of the reactants employed will vary over a wide range. Inorder to effect replacement of two of the hydrogen atoms, the componentsshould be combined so as to have at least two moles of the halo-alkylaromatic acid for every mole of the aromatic compound having the tworeplaceable hydrogen atoms but larger ratios than this can be employedif desired. Preferred ratios vary from 2:1 to 5:1.

The condensation may be accomplished in the presence or absence ofsolvents or diluents. If solvents or diluents are employed, they may bethose that are relatively inert or those that may take part in thereaction. Such solvents include hydrocarbons, such as carbontetrachloride, chloroform, ethylene dichloride, tetrachloroethane, andthe like, and mixtures thereof. If the solvent selected takes part inthe reaction, an excess of that amount required should be employed.

Suitable temperatures to be employed in the process range from about C.to about 150 C. Temperatures much above 150 C. should generally not beemployed as they cause polymerization instead of the formation of thedesired monomeric acids. Preferred temperatures range from about 80 C.to about 140 C. Atmospheric, superatmospheric or subatmosphericpressures may be used as desired or necessary.

The hydrogen chloride formed in the reaction may be removed from thereaction chamber by any of the well known conventional methods. Theacids or derivatives formed in the reaction may be recovered at the endof the process by any suitable method, such as precipitation,filtration, distillation, and the like.

The cycloaliphatic polycarboxylic acids and the acids containing bothcycloaliphatic and aromatic rings may be obtained by hydrogenation orpartial hydrogenation of the above-described aromatic polycarbonylicacids. The hydrogenation is preferably accomplished by con- 4 tacting arelatively water soluble saltof the-aromatic acids, such as an alkalimetal salt, with hydrogen at an elevated temperature and pressure in thepresence of a hydrogenation catalyst, such as Raney nickel. Temperaturesused in this preferred process preferably vary from about C. to about250 C. Preferred pressures vary from about 500 to 1000 pounds per squareinch.

The type of alcohol used in the preparation of the polyesters willdepend on the product desired. If linear polyesters are desired forformation of fibers, one should select a dihydric alcohol, andpreferably an aliphatic dihydric alcohol, such as, for example, ethyleneglycol, diethylene glycol, triethylene glycol, 1,5-pentanediol,hexanediol-1,6, 3-ethyl hexanediol-1,3, glycerol monoallyl ether,2,4-butadien-l,4-diol, 2,8-dodecanediol, thiodipropanol,sulfonyldipropanol, glycerol monobutyrate, 2,S-dimethyl-Z,6-heptanediol,and the like. Particularly preferred alcohols to be used for thispurpose are the alkanediols, thiaalkanediols and oxaalkanediols, andespecially those containing no more than 12 carbon atoms.

If the polyester is to be used in the preparation of coatingcompositions, one should select a polyhydrc alcohol having at leastthree hydroxyl groups, such as, for example, glycerol, hexanetriol,pentaerythritol, mannitol, methyltrimethylolmethane, 1,4,6-octanetriol,1,3,7-heptanetriol, polypentaerythritol, polyallyl alcohol,polymethallyl alcohol, tetrohydroxycyclohexane, trihydroxybenzene,3,5-dithioctanetriol, polyols formed by the condensation of bis-phenolswith epichlorohydrin, and the like. Particularly preferred alcohols ofthis type comprise the aliphatic alcohols possessing from 3 to 6esterifiable hydroxyl groups, and more preferably the alkanepolyols,thiaalkanepolyols and oxaalkanepolyols possessing from 3 to 5 hydroxylgroups and not more than 12 carbon atoms.

The polyesters are formed by merely heating the desired polycyclicpolycarboxylic acid with the polyhydric alcohol, preferably in an inertatmosphere. Ordinarily no catalysts need be employed to effect thisreaction, but, if desired, substances as sulfuric acid,p-tolucnesulfonic acid, zinc chloride, stannic chloride, calciumacetate, barium acetate, and the like, in amounts varying from about0.1% to 5% by weight of reactants may be employed.

The proportion of reactants to be used in the polyester formationreaction may vary depending upon the prop erties desired in finishedproduct. Ordinarily, the polycarboxylic acid will be reacted with atleast a chemical equivalent amount of the polyhydric alcohol. A chemicalequivalent amount as used herein in this regard refers to that amount ofalcohol needed to'furnish one OH group for every carboxyl group.Preferably one reacts the acid withan excess up to 50% excess of thealcohol.

The polyester formation may be accomplished in the presence or absenceof diluents. If solvents and diluents are employed, it is desirable toutilize inert organic compounds, such as benzene, toluene, xylene,cyclohexane and the like, and mixtures thereof.

If trihydric alcohols are employed in formation of alkyd resins for usein coatings and the like it may also be desired to add modifying agentsto the resinous mixture. Modi- 'fying agents are preferablymonocarboxylic acids, such as, for example saturated aliphatic andcycloaliphatic monocarboxylic acids, unsaturated cycloaliphatic andaliphatic monocarboxylic acids, aromatic and substituted aromatic. suchas haloand alkyl-substituted aromatic monocarborylic acids. Examples ofsuch acids include, among others. butyric acid, capric acid,cyclohexanecarboxylic acid, chlorobutyric acid, benzoic acid,p-tert-butyl benzoic acid, 3,5- di-tert-butylbenzoic acid, chlorobenzoicacid, fatty acids derived from natural oils, as drying oils, semidryingoils and nondrying oils, such as linseed, soybean, perilla, tung,walnut, pineseed, olive, oiticica, corn, cottonseed, coc'oanut, hempseed, herring, poppy seed, mustard, peanut, rapeseed, salmon, dehydratedcastor oil, rubber seed, safflower, and the like, and mixtures thereof.

Temperature employed during the polyester formation may vary dependingon reactants. In most cases, the temperature will range between 100 C.and 250 C., with a preferred range of between 200 C. to 230 C.

It is preferred to accomplish the preparation of the resins under ablanket of inert gas, at least during the initial stages of thereaction. By an inert'gas is meant one substantially devoid of molecularoxygen, such as nitrogen, carbon dioxide, helium, methane, and the like.

The water formed during the reaction may be removed during the reactionor at its completion. It is preferably removed during the course of thereaction preferably as fast as it is formed therein. The removal of thewater may be accomplished by any suitable method, such as azeotropicdistillation with components, such as xylene and benzene. The water mayalso be removed by the passage of the inert gas, such as carbon dioxide,through the reaction zone.

If the polyhydric alcohol employed in the reaction contains three ormore hydroxyl groups, there may be danger of gelation and care should betaken to avoid such action. This may be avoided by not overheating andnot heating the mixture too long. To prevent this difficulty, it is bestto follow the course of the reaction by making determinations of theviscosity and acid number on samples withdrawn from the reactionmixture. The heating is then discontinued after the viscosity hasreached the desired value and the acid number has been reduced to avalue between about 5 and 30.

When the reaction is substantially complete, the inert solvents ordiluents, remaining water and uncombined reactants are preferablyremoved from the reaction mixture. Removal is conveniently accomplishedby vacuum distillation, although fractional distillation, precipitation,etc., may also be utilized.

It is also possible to prepare the polyesters of the invention by usingan ester-exchange reaction wherein an ester of the polycarboxylic acidis heated with the desired polyhydric alcohol in the presence of anester-exchange catalyst and the monohydric alcohol formed in thereaction removed as by distillation. Esters of the polycarboxylic acidsused in this reaction are preferably the lower alkyl or alkenyl esters,such as their methyl, ethyl, butyl, allyl, vinyl, pentyl esters, but insome cases higher esters, e. g., their octyl esters, may also beemployed. Suitable esterexchange catalysts that may be used in this typeof reaction include, among others, alkali metal alcoholates, such assodium and potassium alcoholates; metals, such as copper, zinc, lithium,magnesium, such as in the form of powder, shavings, etc.; aluminumalkoxides, sodium phenoxide, and the like, in amounts preferably varyingfrom about .1% to 5% by weight. Proportions of reactants and reactiontemperatures are substantially the same as those described above forstraight esterification reaction.

The polyesters of the invention are high melting solid resins. Theresins prepared from the dihydric alcohols are particularly useful inthat they may be drawn into fibers which can be oriented by colddrawing. The resulting fibers are very strong and pliable and have gooddielectric properties and durability. In addition, they have excellentheat stability and are superior in this regard to many of the commercialpolyester fibers.

The polyesters prepared from the dihydric alcohols and thecycloaliphatic polycarboxylic acids are also useful and valuable asplasticizers for vinyl polymers, such as polymers and copolymers ofvinylidene chloride, styrene, methyl methacrylate and the like. Vinylpolymer compositions containing these polyesters in amounts varying from25 parts to 100 parts over 100 parts of polymer have excellent strengthand flexibility and good resistance to water extraction. Vinyl polymercompositions containing the polyesters also have excellent resistance toloss of plasticizers through evaporation and/ or migration.

Thepolyesters prepared from the alcohols having more than two hydroxylgroups are particularly valuable in the preparation of surface coatingand impregnating compositions. For this application, they may becombined with various coating solvents or oils or may be added tocompositions containing film-forming components such as vinyl polymers,aminoplast resins, cellulose ether and esters and the like. They areparticularly useful in the preparation of baking lacquers and enamels.In this case they are preferably combined with urea-formaldehyde ormelamine-formaldehyde resins and other desired components, such aspigments, plasticizers, stabilizers, and the like, and the mixture thendiluted with solvents or diluents to provide a composition having thedesired viscosity. This composition may then be applied to the desiredsurface and baked at temperatures generally varying from C. to 175 C.The resulting baked films are very hard and have good resistance towater and solvents.

The new cycloaliphatic polycarboxylic acids prepared as described abovehave been found to have other unique and valuable properties in additionto their use in preparation of the claimed polyesters. They findapplication as additives for lubricating compositions, greasecompositions, herbicidal, fungicidal and insecticidal compositions aswell as additives for various impregnating compositions.

The new cycloaliphatic polycarboxylic acids may also be used to preparevaluable derivatives, such as monomeric esters and amides as well aspolyamides. The monomeric esters and amides are particularly valuable asplasticizers for vinyl halide polymers as they have a high degree ofcompatibility with these polymers and the resulting compositions havegood strength and flexibility over a wide range of conditions. Inaddition, the esters and amides are not easily lost from thecompositions through vaporization or migration and the plasticizedcompositions are able to withstand long periods of exposure to hightemperatures without shrinking or becoming embrittled.

The monomeric derivatives containing a polymerizable linkage, such asthe ethylenically unsaturated esters and amides, as the allyl and vinylesters and the N-alkenyl substituted amides, may also be polymerized toproduce valuable thermosetting polymeric materials. Those derivativescontaining at least two unsaturated linkages can be polymerized toproduce especially valuable thermosetting products. The polymerizationis preferably accomplished by merely heating the derivatives in thepresence of a peroxide catalyst, such as benzoyl peroxide, tert-butylhydroperoxide, tert-butyl perbenzoate, cymene hydroperoxide, tert-butylper-acetate, and mixtures thereof, in amounts preferably varying fromabout 1% to 5% by weight. The polymerization may be effected in bulk, inthe presence of solvents or diluents, or in an aqueous emulsion orsuspension.

To illustrate the manner in which the invention may be carried out, thefollowing examples are given. It is to be understood, however, that theexamples are for the purpose of illustration and the invention is not tobe regarded as limited to any of the specific conditions or reactantscited therein. Unless otherwisespecified, parts described in theexamples are parts by weight.

Example I About 45.5 parts (0.267 mole) of 4-chloromethylbenzo1c acid iscombined with 10 parts (0.128 mole) of benzene and 8 parts of ferricchloride and the resulting mixture gradually warmed. There is a rapidevolution of hydrogen chloride as the temperature approaches C. and whenit reaches 139 C. no further gas is liberated. A titration showed that96% of the required hydrogen chloride has been formed. The reactionmixture is then cooled and shaken with 5% sodium hydroxide. The aqueousphase is filtered, treated with 'charcoal and then acidified. Theresidue is then treated with hot water and recrystallized from alcohol.The

resulting product is a white, crystalline solid having a melting pointof 260-280 C. The acid is identified as dicarboxydibenzylbenzene (HOOC HCH C H CH C H COOH) Anal. Calcd. for C H O C, 76.3%; H, 5.20. Found:

About 35 parts (.1 mole) of the dicarboxydibenzylbenzene produced aboveis mixed with 49.7 parts (.8 mole) of ethylene glycol and 1 part ofconcentrated sulfuric acid and the mixture gradually heated up to 170 C.and then held in the range of 170 C. to 230 C. until the reaction iscomplete. A slow stream of carbon dioxide is sent through the charge toeliminate the air and carry away the water of esterification. The excessglycol is then removed under reduced pressure. The resulting product isa high melting light brown solid resin. The resin could be drawn intofibers which could be permanently oriented by cold drawing. The fibershave excellent heat stability and did not decompose at temperatures ashigh as 375 C.

Example II About 35 parts of the dicarboxydibenzylbenzene produced as inExample I is mixed with 85 parts of diethylene glycol and 1 part ofsulfuric acid and the mixture gradually heated up to 225 C. and held atthat temperature until the reaction is complete. A slow stream of carbondioxide is sent through the charge to eliminate the air and carry awaythe water of esterification. The excess glycol is then removed underreduced pressure. The resulting product is a high melting light yellowsolid resin. The resin could be drawn into fibers which could bepermanently oriented by cold drawing. The fibers have excellent heatstability and do not decompose at temperatures as high as 375 C.

Example III A potassium salt of dicarboxydibenzylbenzene produced as inExample I is prepared by dissolving 500 parts of the polycarboxylic acidin 1000 parts of potassium hydroxide solution. About 10 parts of Raneynickel is then added to 200 parts of the above-described solution andthe resulting mixture exposed to 1500 pounds hydrogen pressure at atemperature between 150 C. and 175 C. When no further reduction inpressure takes place, the product is recovered by filtration andsubsequently acidified. The solid that separates is filtered and dried.The solid that is recovered after recrystallizatron from dilute alcoholis identified as di(carboxycyclohexylmethyl) cyclohexane.

About 32 parts of the di(carboxycyclohexylmethyl) cyclohexane is mixedwith 52 parts of 1,5-pentanediol and 1 part of concentrated sulfuricacid and the mixture gradually heated up to 225 C. and held at thattemperature until the reaction is complete.

bined with 60 parts of benzene and 10 parts of ferric chloride and theresulting mixture gradually warmed.

Hydrogen chloride is liberated as the temperature zapproaches'125 C. andwhen it reaches 140 C. no further gas is liberated. After the reactionis complete, the mixture is cooled and shaken with 5% sodium hydroxide.The aqueous phase is filtered, treated with charcoal and then acidified.The residue is then treated with hot water and recrystallized fromalcohol. The resulting product is a white crystalline solid meltingabove 280 C. and identified as di(carboxyphenylethyl) isopropylbenzene.

About 39 parts of the di(carboxyphenylethyl) isopropylbenzene producedas above is mixed with 56 parts of thiodipropanol (HOCH CH CH SCH CH CHOH) and .5 part concentrated sulfuric acid and the mixture graduallyheated up to 200 C. and held at that temperature until the reaction iscomplete. A slow stream of carbon dioxide is sent through the charge toeliminate the air and carry away the water of esterification. The excessthiodipropanol is then removed under reduced pressure. The resultingproduct is a high melting light brown solid resin. The resin can bedrawn into fibers which can be permanently oriented by cold drawing. Thefibers have excellent heat stability and do not decompose attemperatures as high as 375 C.

Example V 900 parts of dicarboxydibenzylbenzene produced as in ExampleI, 240 parts of glycerol and 360 parts of dehydrated castor oil areplaced in a reaction flask equipped with a stainless steel stirrer,nitrogen bubbler, thermometer and phase separating condenser. Xylene isused to remove the water azeotropically. The charge is brought to acooking temperature of 250 C. and held at that temperature till thereaction is complete. The resulting polyester had an acid number of 5 to8 (mg. KOH g.).

A white baking enamel is prepared by combining parts of titaniumdioxide, 50 parts of the polyester prepared above and 50 parts of abutylated melamine-formaldehyde resin (Melmac 248-8) and adding xyleneto obtain the desired viscosity.

The above-described enamel is sprayed on cold roll steel panels to forma film having thickness of 1 to 1.5 mils and the films are baked for 12minutes at 160 C. The resulting films are very hard and have goodresistance to water and solvents.

Example V1 830 parts of di(carboxycyclohexylmethyl) cyclohexane producedas in Example HI, 350 parts of 1,2,6-hexanethiol and 362 parts ofcocoanut fatty acids are placed in the reaction flask described in thepreceding example with toluene as the azeotrope former. The charge isbrought to a cooking temperature of 230 C. and held at that temperaturetill the reaction is complete. The resulting product is a light brownsolid having an acid number of 810.

A clear lacquer composition is prepared by combining 40 parts of thepolyester produced above with 60 parts of a melamine-formaldehyde resin(Melmac 2488) and add ing toluene to form the desired viscosity.

The above-described lacquer is then flowed out on tin plate panels toform a film having thickness of 1 mil. These panels are then baked for30 minutes at C. The resulting films are hard and flexible and have goodresistance to water and solvents.

We claim as our invention:

1. A resinous polyester of a polycarboxylic acid having a linear chaincontaining at least three six-membered carbocyclic rings which arejoined together in series by bivalent aliphatic hydrocarbon radicalswhich contain only carbon-to-carbon linkages and having at least twocarboxyl groups attached to separate carbocyclic rings, and a polyhydricalcohol.

2. A resinous polyester as defined in claim 1 wherein the carbocylicrings in the acid molecule are aromatic rings.

3. A resinous polyester as defined in claim 1 wherein the carbocyclicrings in the acid molecule are cycloaliphatic rings.

4. A resinous polyester as defined in claim 1 wherein the polyhydricalcohol is an aliphatic dihydric alcohol.

5. A resinous polyester as defined in claim 1 wherein the polyhydricalcohol is an aliphatic polyhydric alcohol possessing from 3 to 6hydroxyl groups and not more than 12 carbon atoms.

6. A linear resinous polyester of a polycarboxylic acid having a linearchain containing at least three six-membered carbocyclic rings which arejoined together in series by bivalent aliphatic hydrocarbon radicalswhich contain only carbon-to-carbon linkages and having two carboxygroups attached to different rings, and an aliphatic dihydric alcohol.

7. A resinous polyester 'as defined in claim 6 wherein the acid isdicarboxydibenzylbenzene.

8. A resinous polyester as defined in claim 6 wherein the alcohol is analkanediol.

9. A resinous polyester as defined in claim 6 wherein the alcohol is apolyethylene glycol.

10. A resinous polyester of a polycarboxylic acid having a linear chaincontaining three six-membered carbocyclic rings which are joinedtogether in series by hivalent alkylene radicals which contain onlycarbon-tocarbon linkages and having two carboxyl groups attached todifierent rings, and aliphatic polyhydric alcohols containing no morethan 12 carbon atoms.

11. A resinous polyester as in claim 10 wherein the acid isdi(carboxycyclohexylmethyl) cyclohexane and the alcohol is1,5-pentanediol.

12. A resinous polyester as in claim 10 wherein the alcohol isthiodipropanol.

13. A resinous polyester as in claim 10 wherein the acid isdicarboxydibenzylbenzene and the alcohol is glycerol.

14. A resinous polyester of a polycarboxylic acid having a linear chaincontaining three six-membered carbocyclic rings which are joinedtogether in series by hivalent alkylene radicals which contain onlycarbon-tocarbon linkages and having two carboxyl groups attached todifierent rings, and an aliphatic alcohol containing at least threehydroxyl groups, said polyester being modified with a monocarboxylicacid.

15. A resinous polyester of dicarboxydibenzylbenzene and ethyleneglycol.

OTHER REFERENCES Weiss et al.: Beilstein, 4th edition, 2nd supplement,volume 9, page 696 (1949).

1. A RESINOUS POLYESTER OF A POLYCARBOXYLIC ACID HAVING A LINEAR CHAINCONTAINING AT LEAST THREE-SIX-MEMBERED CARBOCYCLIC RINGS WHICH AREJOINED TOGETHER IN SERIES BY BIVALENT ALIPHATIC HYDROCARBON RADICALSWHICH CONTAIN ONLY CARBON-TO-CARBON LINKAGES AND HAVING AT LEAST TWOCARBOXYL GROUPS ATTACHED TO SEPARATE CARBOXYLIC RINGS, AND A POLYHYDRICALCOHOL.